Comparison Between ImmunoCAP And RAST For Diagnosis Of Hypersensitivity To Betalactams

RATIONALE: In vitro tests have shown to be helpful in the diagnosis of betalactams (BL) hypersensitivity, being immunoassays the most widely used. Our aim was to compare sensitivity, specificity, positive and negative predictive value (PPV and NPP) of both immunoassays in the diagnosis of BL hypersensitivity.

METHODS: We included 37 patients with confirmed immediate hypersensitivity to penicillin/amoxicillin by basophil activation test (BAT), skin tests (ST) and/or drug provocation test (DPT). ImmunoCAP and RAST were performed with penicillin and amoxicillin in all patients as well as in 20 tolerants to BL.

RESULTS: Comparing RAST and CAP, sensitivity was higher for RAST (67% vs 15.7%, p<0.0001) whereas specificity was higher for CAP (100% vs 50%, p=0.0002). Sensitivity was higher for RAST compared to CAP considering both penicillin (9% vs 0%, p>0.05) and amoxicillin (61% vs 15.7%, p<0.0001). PPV was higher for CAP compared to RAST (100% vs 81%, p>0.05), whereas NPV was higher for RAST than for CAP (34% vs 21%, p>0.05). A concordant result between the two assays was found in 16 cases (43.24%: kappa=0.27), which represents a fair level of agreement. RAST was positive in 75% of patients with negative ST, thus by combining RAST and ST we can diagnose 91.8% of patients with immediate hypersensitivity to BL.

CONCLUSIONS: Immunoassays represents useful complementary tools for diagnosing HRs to BL, being RAST more sensitive than CAP. When combined RAST with ST, we can diagnose correctly most of patients with immediate hypersensitivity to BL.